Contact making and breaking device



July 5, 1955 H. A. NICKELL ET AL CONTACT MAKING AND BREAKING DEVICEFiled April 26, 1952 m X4? l j or 1 HSPShGH A.NioKH Thomas I. Maslir'l Mwmn Their Attorney United States Patent CONTACT IVIAKING AND BREAKINGDEVICE Hershell A. Nickell, Alplaus, and Thomas I. Maslin,

Schenectady, N. Y., assignors to General Electric Company, a corporationof New Yuri-r Application April 26, 1952, Serial No. 284,525

3 Claims. (Cl. 200-166) This invention relates to improvements incontact making and breaking devices and more particularly toimprovements in pushbutton switches.

A primary object of the invention is to elfeet simultaneous separationof both ends of a contact bridging member from its cooperatingstationary contacts in response to contact opening movement of anactuating member in order to produce even distribution of arcing on allcontacts and thereby lengthen their useful lives.

In carrying the invention into effect in one form thereof, a pair ofstationary contacts are mounted in spaced apart relationship and withtheir contacting surfaces approximately in the same plane. They arebridged by a movable bar which, at its ends, is provided with contactswhich mate with the stationary contacts. An actuating member is disposedbetween the stationary contacts for movement normal to the plane oftheir contacting surfaces. Between its ends, the bridging member isprovided with an arcuate curved portion having its center of curvatureapproximately equidistant from the ends of the bridging member toprovide for simultaneous separation of both ends of the bridging memberfrom the stationary contacts in response to contact opening movement ofthe actuating member.

For a better and more complete understanding of the invention, referenceshould now be had to the following specification and to the accompanyingdrawings, of which Fig. l is a view in front elevation of an embodimentof the invention in a pushbutton switch with a part of the contact blockcasing broken away, Fig. 2 is a side elevation with a portion of thecontact block broken away, Fig. 3 is a plan view in section taken on thelines 3-3 of Fig. l, and Figs. 4 and 5 are enlarged views of details.

Referring now to the drawing, the switch comprises a two-piece moldedinsulating block having identical halves 1 and 1a. Preferably, the blockis made of a high are resistant compound. The halves 1 and 1a arerecessed to receive and to provide for sliding movement of a plunger oractuating member 2 which is molded of the same insulating compound.

An opening 3, a section of which has the shape of a non-rectangularparallelogram, extends through the plunger. A pair of contact bridgingmembers 4 and 5 are mounted in the opening 3 and are biased apart bysuitable means such as a spring 6.

One end of the plunger is provided with a projection 7 having a roundedend surface which is adapted to be engaged by an operating washer (notshown) of a pushbutton unit.

The inside opposing walls of the halves 1 and 1a of the contact blockare provided with positioning indentations 8 which receive the ends of apair of spaced apart, normally closed stationary contacts 9 and 10, anda pair of spaced apart, normally open stationary contacts 11 and 12.These contacts have terminals 9a, 10a, 11a and 12a which fit snugly intoslots in the side walls of the block through which they project to theoutside.

As shown, the stationary contacts are provided with contact tips 912,iilb, 11b and 12b, which are made of a good electrical conducting andhigh oxidation resistant metal such as silver. Similarly, the ends ofthe movable bridging contact members 4 and 5 are provided with silvertips 4a, 4b, 5a and 5b which mate with stationary contact tips 9b, 10b,11b and 12!) respectively.

The lower end of the plunger 2 is provided with a cylindrical recess 13which receives one end of a return spring 14. A spring retaining Washer15 rests against a circumferential shoulder 1-6 at the lower end of therecess in which the plunger slides.

Intermediate their ends, the movable bridging contact bars 4 and 5 areprovided with arcuate curve-shaped portions 4c and 5c having centers ofcurvature 4d and 5d which are equidistant from the ends of the bars.Consequently, these centers of curvature lie in a central axial planewhich is perpendicular to lines joining the stationary contacts 9b and19b and stationary contacts 11b and 1211. These centers of curvature arelines which are parallel to each other and which are perpendicular tothe plane which contains the centerlines of all of the contacts, whichin the particular embodiment illustrated in the drawing is also thecentral dividing plane between the two halves 1 and 1a of the contactblock.

The convex surfaces of the arcuate curve-shaped portions of the contactbridging bars are illustrated as being serrated. It is contemplated,however, that these surfaces may be made smooth.

When no force is exerted against the rounded end of the plunger, thereturn spring 14 biases the plunger to the position in which it isillustrated in Figs. 1, 2, 4 and 5 of the drawing, with the movablecontact tips 4a and 4b engagirs their mating stationary contact tips 912and 10b and with movable contact tips 5a and 511 out of engagement withtheir respective mating stationary contact tips 11b and 12b. The forceof the return spring 14 is greater than the force of the wipe spring 6.Consequently, after the moving contacts 4:: and 41) have engaged theirmating stationary contacts 912 and 165, the wipe spring 6 is furthercompressed and the upper contact bar engaging surface 2a of the plungeris I separated and moved upward from the arcuate portion 40 of contactbar 4 until the shoulder 2b of the plunger comes to rest against aninternal shoulder of the contact block. This separation of the engagingsurface from the contact bar provides lost motion which must be taken upwhen the plunger is depressed before engagement is effected between theengaging surface of the plunger and the contact bar.

Pushbutton switches are generally produced by mass production methods inorder to realize the maximum possible economy in manufacture. As aresult of such mass production methods, slight inaccuracies are found inthe finished product which may lead to undesirable results. For example,in the manufacture of pushbutton switches, such as described in theforegoing, varying amounts of misalignment of the stationary contactswill usually be present. This is illustrated in Fig. 4 in which thecontacting surfaces of stationary contacts 917- and 1% are not coplanar,i. e., do not occupy the same plane. The result is that when the movablecontact tips engage their mating stationary contact tips, the contactbar is skewed or tilted so that its longitudinal axis is not parallel tothe upper contact bar engaging surface 2a of the plunger.

Consequently, if the contact bar 4 were made in the conventional form,i. e., perfectly straight from end to end, first contact between theplunger and the contact bar in response to depression of the plungerwould be gaging surface of the plunger with the upper surface of thecontact bar. This meeting would take place along the line 4e which isobserved in Fig. 4 as a point. Thus,

' the contact bar would become a lever having a fulcrum 90 on themeeting line of the stationary contact 9b and moving contact 4a. Furtherdepression of the plunger would effect clockwise rotation of the contactbar 4 about fulcrum 9c and cause separation of contacts ib and 10b.prior to separation of contacts 4:: and 9a. Consequently, the arcing atthe contact tips would be uneven with by far the greater part of thearcing taking place at contact tips 4b and 16b, which separated prior tothe separation of contacts tips 4a and 9b.

However, as a result of the presence of the arcuate curved portion 40,the actuating surface 20 of the plunger engages the arcuate curvedsurface on the line 4f, which is observed in Fig. 5 as a dot. Thismeeting line lies in central plane which is defined by the centerlinesof curvatures 4d and 5d and is parallel to these lines. Consequently, asthe downward movement of the plunger is continued, there is no tendencyfor the contact bar to rotate about the meeting line 90 or the meetingline 100 as a fulcrum. The result is that both contact tips 4a and 4bseparate from their mating contact tips 91) and 1% simultaneously, andthe arcing is evenly distributed between both pairs of contact tips.This even distribution of the arcing between both pairs of matingcontact tips reduces the duty on each pair and greatly lengthens theiruseful lives. Actual tests prove that the useful life of the contacttips is double that of contact tips in similar switches havingconventional contact bars which are rectilinear from end to end.

The self-aligning operation with respect to arcuate portion 5c ofcontact bar 5 and contact bar engaging surface 2b is identical with thatjust described.

Although in accordance with the provisions of the patent statutes, thisinvention is described as embodied in concrete form and the principlethereof has been described, together with the best mode in which it isnow contemplated applying that principle, it will be understood thatalterations and modifications will readily suggest themselves to personsskilled in the art without departing from the true spirit of thisinvention or from the scope of the annexed claims.

What we claim as new and desire to secure by Letters Patent of theUnited States is: I

1. In a contact making and breaking device, a pair of stationary spacedapart contacts having their contacting surfaces approximately in thesame plane, a movable actuating member disposed between said contactsfor movement substantially normal to said plane, and having a planarsurface, a bridging contact member providing intermediate its ends anarcuate portion with the extremities of its are extending toward saidends and presenting its convex face toward said surface of saidactuating member to provide for simultaneous separation of both saidends from said stationary contacts irrespective of misalignment of saidstationary contacts in response to contact opening movement of saidactuating member and engagement of said surfaces.

In a contact making and breaking device, a pair of stationary spacedapart contacts having their contacting surfaces approximately in thesame plane, a movable actuating member disposed between said stationarycontacts for movement substantially normal to said plane and having aplanar movable contact actuating surface substantially parallel to saidplane, a movable contact bridging member, and means for effectingsimultaneous separation of the ends of said bridging member from saidstationary contacts in response to contact opening movement of saidactuating member comprising an intermediate arcuately curved portion ofsaid bridging member presenting its convex surface toward said movablecontact actuating surface and having its center of curvatureapproximately equidistant from said ends and the extremities of its areextending toward said ends.

3. in a contact making and breaking device, a pair of stationary spacedapart contacts having their contacting surfaces approximately in thesame plane, a movable actuating member disposed between said stationarycontacts for movement substantially normal to said con tact surface andhaving a planar movable contact actuating surface, a movable contactbridging member mounted on said actuating member, means for effectingsimultaneous separation of the ends of said bridging member from saidstationary contacts in response to contact opening movement of saidactuating member comprising an intermediate arcuately curved portion ofsaid bridging member presenting its convex surface toward said movablecontact actuating surface and having its center of curvatureapproximately equidistant from said ends, and means providing lostmotion between said actuating member and said bridging member comprisingmeans for biasing said engaging surface out of engagement with saidbridging member in the contact closing position of said bridging member.

References Cited in the file of this patent UNITED STATES PATENTS

